Epidemiological data demonstrates strong gender bias in hepatocellular carcinomas. This phenomenon cannot not be attributed to gender differences in life style factors. Moreover, there is no evidence implicating direct effect of sex hormones in the tumor growth and dissemination. We hypothesize that a "feminization" of the phenotype of hepatocellular carcinoma is a result of reciprocal interaction between tumor and metabolic milieu of the host organism mediated through yet unknown, sex hormone-independent pathways. In order to dissect molecular mechanisms responsible for sexually dimorphic behavior of hepatocellular carcinoma we propose to utilize serially transplantable tumors in a clonal zebrafish model recently developed in our lab. A second and closely related goal is to use this novel system as a tool for investigation of developmental aspects of tumor-host relationships focusing on changes in the tumor behavior and gene expression signatures in different developmental contexts of the host organism. Zebrafish with distinct developmental stages of gender formation provides an excellent system for investigation of such mechanisms. Our preliminary data strongly support a notion that hepatomas retain considerable phenotypic plasticity which pertains to tumor behavior. By using different carcinogens and treatment protocols we will generate a broad spectrum of hepatic tumors, including transplantable triploid liver tumors. The molecular signatures of these tumors will aid in the design of novel transgenic models of hepatocellular carcinomas. These transgenically-induced tumor lines expressing fluorescent tags will further facilitate in-depth analysis of invasive tumor growth, angiogenesis and metastasis by in vivo imaging. The latter technology will be enhanced by generating transparent clonal zebrafish lines which will facilitate assessment of the spatial and temporal progression of hepatomas in a sexually dimorphic manner. A comparison of gene expression profiles of these tumors transplanted to syngeneic fish of either gender at different maturational stages will delineate gender-specific molecular pathways that either promote or counteract development of hepatocellular carcinoma. Overall, this model based on clonal zebrafish lines established in our lab will yield a novel targets for experimental therapy of hepatocellular carcinoma which remains a tumor with poor prognosis and significant initial or acquired chemoresistance. PUBLIC HEALTH RELEVANCE: Environmental guidance of tumor cell phenotypic plasticity provides a novel tool for antitumor therapy. In this proposal we will attempt to highlight the dominant role of the microenvironment in the regulation of sexual dimorphism of hepatic tumors. Further understanding the complex interaction between the tumor cell and its microenvironment is essential in order to develop focused therapeutic strategies to improve tumor treatment outcomes.